1. Field of the Disclosure
The invention generally relates to regulators and more specifically to regulators having an adjustable fixed pressure relief assembly.
2. Related Technology
Fluid flow from one location to another location is often controlled by a valve or regulator. The valve or regulator may be designed to maintain certain flow rates or fluid pressures within a predetermined range. A regulator includes an actuating mechanism that controls a location of a valve plug with respect to a valve seat. The valve plug and valve seat cooperate to control fluid flow through the valve or regulator.
In some environments, such as gas tank operations, the potential exists for fluid pressure to build up to dangerous levels. For example, in the natural gas or propane industry, a regulator valve may control the flow of natural gas or propane out of a tank. As the temperature of the natural gas or propane within the tank increases, the pressure of the natural gas or propane will also increase. If the pressure exceeds a design pressure for the regulator or the tank, material failure may occur, causing danger to lives and property. Thus, most regulators attached to tanks have some sort of pressure relief device either attached to the tank or on the regulator itself.
In some regulators a pressure relief assembly may be located in an actuator housing. The pressure relief assembly includes an actuator stem, a diaphragm plate, a relief plate, and a diaphragm at least partially disposed between the diaphragm plate and the relief plate. A relief spring is disposed between a relief spring seat and the relief plate, the relief spring biasing the relief plate towards the diaphragm, a releasable seal being formed between the diaphragm and the relief plate. Generally speaking, there are two types of relief assemblies, a fixed assembly and an adjustable assembly. The fixed assemblies include a relief spring seat that is fixed to the actuator stem and not movable relative to the actuator stem. Fixed assemblies are set to a single relief pressure and are not adaptable for other set points. However, fixed assemblies are very reliable.
Adjustable assemblies, on the other hand, include an adjustable relief spring seat that is movably attached to the actuator stem with a compression nut. The adjustable relief spring seat may be moved along the actuator stem to adjust a bias generated by the relief spring. Adjustable assemblies are more flexible and may be adapted to different relief pressures. However, adjustable assemblies are more susceptible to failure as the relief spring seat may unexpectedly move along the actuator stem if the compression nut becomes loose. For this reason, adjustable assemblies are less reliable and some regulations prevent the use of adjustable assemblies for certain uses.